Non-aqueous vinyl dispersion coating compositions have particular advantage as protective coatings in that they offer formability, weatherability, and chemical and mechanical wear resistance. They generally comprise high molecular weight particulate polymers of vinyl chloride and are often referred to as organosols and plastisols.
Some have characterized such coating compositions as "plastisols" if they are free of volatile solvent and diluent, and "organosols" if they contain volatile solvent and diluent. As used herein and when used in the appended claims the terminology "plastisol" is used in the more practical sense, namely any vinyl dispersion composition containing up to about 10% by weight volatiles. "Organosol" as that term is used herein, refers to compositions having greater than 10% by weight volatiles, e.g. low molecular weight ketones, esters and aliphatic and aromatic hydrocarbons, and can be considered volatile thinned plastisols. Vinyl dispersion coating compositions include, likewise, both organosols and plastisols.
Vinyl dispersion coating compositions basically comprise a particulate vinyl resin (normally polyvinylchloride homopolymer and often vinyl chloride-vinyl acetate copolymer) dispersed in a liquid phase comprising plasticizer therefor, and optionally solvent and diluent as well as other ingredients including pigment, filler, solution resin, surfactant and other adjuvants. If hydrophilic surfaces are to be coated, it is known that phenolic adhesion promotors may be advantageously employed.
These phenolic adhesion promotors, comprising a phenol-formaldehyde condensate made with molar excess phenol and a formaldehyde producing compound, have not been altogether satisfactory, particularly when thin film, e.g. up to 2 mm., coatings are made. According to an important aspect of this invention, thin film adhesion of vinyl coatings is dramatically improved, up to five times or more as compared to vinyl dispersion coatings which include conventional adhesion promotors. Such increased thin film adhesion can become also important when considering failures of even thick films at its thin film edges.